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Drain flies

Drain flies are grayish gnats that are 2 mm to 3 mm in length, massive and fuzzy in appearance. These little flies look like moths, which explains why they are sometimes called moth flies. They live two weeks when the conditions are ideal.

They are usually not harmful but they can become a real nuisance when they find a place with decomposing organic matter that is sitting in standing water. That is why we often see these flies around drains, sewers, sinks, sanitary facilities, compost, gutters and septic tanks. 

Active mainly at night, drain flies search for organic debris on which they feed and lay their eggs. They can often be found in the biofilm created by an accumulation of water and debris in the corners and joints of drain pipes.

Development and Behaviours

The female lays her eggs in clusters of 30 to 100 eggs and these hatch 2 days later. Drain fly larvae develop in organic matter that forms on the walls of the drains. The larval stage normally lasts 10 days and the pupa stage takes a maximum of 40 hours. Once their development is complete, adult drain flies can reproduce. The drain fly has a life expectancy of around 2 weeks.


Here are some preventative tips to help you prevent a drain fly infestation:

  • Repair water leaks quickly
  • Regular maintenance of drains to prevent organic matter from accumulating
  • Fill holes and cracks (drain pipes, walls, etc.)
  • Clean the drains using a brush and a drain cleaner
  • Take out the trash regularly
  • Get rid of stagnant water sources
  • Clean your pipes to avoid water drainage problems
  • Do not leave food lying around
  • Check that there is no humid areas inside your property

Contact an exterminator to obtain a protection program


It is important to react quickly when you notice the presence of drain flies because they reproduce very quickly. The key to controlling a drain fly infestation often resides in sanitary maintenance recommendations.  Our pest management technicians are experienced in the development of long-term control solutions to solve this type of infestation. Do not hesitate to contact V Extermination for all your pest control needs. We guarantee safe, effective and fast treatment!

Fly infestation?